1. Field of the Invention
The present invention relates to a light guide used for guiding illumination light and an endoscope for illuminating an object under observation by the illumination light guided by the light guide and observing the object.
2. Description of the Related Art
There are two types of endoscope, that is, for medical use in observing inside of the body cavity of a patient and for industrial use in observing a water pipe or the like. It is generally dark in the body cavity or the like to be observed by the endoscope, so illumination from an external source is required for the observation. As illumination means of the endoscope, a light guide is typically used. The light guide is composed of a large number of optical fibers tied in a bundle. In the light guide, illumination light incident from an end (incident end) of the light guide is emitted from the other end (light emission end).
Conventionally, various actions have been attempted in order to improve an illumination state in the endoscope. A main action is to make the light distribution of illumination as even as possible in a range from a central region in a field of view to a peripheral region. In general, the illumination using the light guide tends to be too bright in the central region in the field of view in comparison with the peripheral region. Therefore, various proposals for improving an illumination optical system provided at the light emission end of the light guide have been conventionally made. By the effects of the conventional proposals, the light distribution has become even, but the light distribution may be required to become evener.